A team of scientists from BC, Alberta and England have, for the first time, decoded the complex genetic makeup of the hard-to-treat, deadliest form of breast cancer. Dr. Sam Aparicio of the B.C. Cancer Agency, who led the study, is pictured in his lab in 2009.

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VANCOUVER — Scientists from British Columbia, Alberta and England have, for the first time, decoded the complex genetic makeup of the hard-to-treat, deadliest form of breast cancer.

Study leader Dr. Sam Aparicio of the BC Cancer Agency, and 58 other researchers, published their findings about triple negative breast cancer (TNBC) in the prestigious journal Nature on Wednesday. The scientists took about 18 months to examine more than 100 human tumours and found huge variations among them, with an unprecedented number and type of genetic and biological abnormalities.

TNBC accounts for about 16 per cent of all breast cancers but 25 per cent of all deaths from breast cancer. It derives its name from the fact that it is missing a trio of surface cell hormone, steroid and protein receptors — estrogen, progesterone and herceptin. When the receptors are present, treatments — such as anti-estrogen therapy — can be used in a bid to inhibit tumour cell growth.

Anti-estrogen drugs interfere with the receptors, which prevents the hormone from attaching or landing on the tumour. In the case of estrogen, it appears to encourage the growth of some types of breast tumours. But in cancers like TNBC, where the tumour is not affected very much, or at all, by estrogen to begin with, anti-estrogen treatment has little or no benefit.

Steven Jones, a co-author of the study, Simon Fraser University professor and head of bioinformatics research at the BC Cancer Agency, said scientists expected to see genetic similarities in the tumours when they mapped their genomes.

But they didn't find the similarities they expected.

"Seeing these tumours at a molecular level has taught us we're dealing with a continuum of different types of cancer here, not just one," he said.

A news release issued by the journal elaborates: "Some tumours only display a few mutations, and involve a limited number of molecular pathways that are implicated in disease progression, whereas multiple mutations and pathways are involved in other tumours," referring to the findings that will most certainly convince experts that in order to do better research and improve the effectiveness of treatment, each tumour is so different that they should probably all be genetically sequenced so treatment can be tailored to each patient.

Genetic sequencing is not the standard of care in Canada and other countries yet, largely because of cost and other resource issues. As well, treatments have not yet caught up with genetic sequencing technology.

The study says TNBCs are still treated as if they were one type of disease even though the latest research shows that these types of breast cancers "do not behave as a single entity in response to current therapies," Jones said, adding the findings show doctors cannot presume that one therapy can treat all tumours under the TNBC umbrella.

"The genetic diversity of these tumours, even though they're clinically similar, probably explains why they are so difficult to treat," Jones said, in an news release.

The $2-million study was a collaboration between scientists at BCCA, the University of British Columbia, Simon Fraser University, Cross Cancer Institute of Alberta, Cancer Research U.K./University of Cambridge and other cancer research agencies.

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